Currently, commercial processes which apply swatches to a sheet, such as shown in Lerner, et al., U.S. Pat. No. 4,061,521 and US2002/0129893 A1 (Winter), and depending on the type of job, provide a relatively high speed operation (e.g., 4,500 sheets per hour) in which blank sheets are fed continuously through operating stations including an adhesive applying station and one or more swatch applying stations where swatches are applied to the sheet.
In making swatch bearing sheets with high process speeds, blank sheets have been pushed by feed fingers (Lerner) or pulled (Winter) by grabbers through the adhesive applying station and the swatch applying stations on top of travel surfaces, at least some of which include upstanding guide portions on one side of the travel surfaces. In the pushing method, these side sheet guides have been spaced apart a distance corresponding to the width of the sheet to ensure the sheets maintain proper alignment as they were pushed by pushing feed fingers through the adhesive applying station and the swatch applying stations. Multiple side sheet guides were required throughout the swatch applying machinery to maintain the sheets in proper alignment. Side sheet guides had been placed before and after the adhesive applying station and each swatch applying station to keep the sheets aligned as they are pushed between stations. Pushing sheets at their trailing edges by pushing feed fingers, without the sheet guides, risked skewing the sheets sideways. This resulted in misfeeds and/or sheets having misaligned swatches. Similar problems may occur with grabbing and pulling sheets downstream by the leading or down stream edge of the sheet.
The feed fingers that pushed the sheets along the travel surfaces in the pushing method were attached to conveyors in the form of drive chains. Separate drive chain conveyors extended between each of the operating stations so that several sets of feed fingers pushed the sheets during their travel from the infeed to the outfeed of the sheets from the machine. The use of multiple sets of conveyers and multiple sets of feed fingers to push each sheet to and from each operating station required precise coordination of the timing of the positions of each set of feed fingers on each conveyor to push the sheet through the operating stations, particularly where operating speed is maximized. Further, the coordination necessary to push a sheet to an operating station with a first set of feed fingers on a first conveyor and then to have a second set of feed fingers on a second conveyor positioned to push the sheet from the operating station had to be precisely timed because errors in the coordination risked misfeeds or misprinted sheets, requiring the machinery to be stopped to correct the errors and reducing the production efficiency of the machinery.
Pushing feed fingers did not positively grip the sheets. Without positive gripping, the feed fingers extended a relatively high distance above the travel surfaces to ensure that they contact the rearward edge of the sheets as occasionally the sheets would not be lying flat on the travel surfaces, for example a curled rearward edge.
Because of the height that the feed fingers extended above the travel surfaces and the lack of positive gripping of the sheets, the feed fingers were not able to push the sheets through the stations. More specifically, upper and lower rollers cooperate to form nips of the operating stations into which the sheets are fed and from which they are discharged. In the nips, adhesive and swatches are applied to the sheets. The height of the feed fingers did not allow for their passage under and through the nip areas between the closely spaced rollers or anvil work surfaces of the operating stations.
Accordingly, instead of using a single set of pushing feed fingers to push the sheets through each operating station, separate sets of pushing feed fingers to push each of the sheets to each station had to be used. The nip formed by the rollers in each station drew the sheets therethrough and discharged them downstream to the next conveyor at which point another set of pushing feed fingers then pushed the sheets to the next station. The timing of the multiple sets of feed fingers had to be coordinated so that as a sheet left a station a new set of feed fingers were positioned to push the sheet to the next station. If the timing was not correctly coordinated, misfeeds occurred. Misfeeds were undesirable because the swatch applying machinery had to be stopped for removal of the misfed sheets and the machinery reset for continued operation.
The swatch applying machinery had to accommodate sheets of different sizes. With changes in paper size, especially when sheets were pushed through work stations, side sheet guides and associated travel surfaces had to be readjusted to maintain the different sized sheets in proper alignment as they traveled. Readjusting sheet guides is labor intensive and could consume as much as four hours creating of labor and equipment down time. When pulling the sheets through the work stations with grippers, a change in paper size risked mispositioning the grippers laterally along the leading edge of the sheet being pulled by the grabbing jaws.
Feeding sheets through work stations at high speeds creates the problem of sheet float. When sheets were pushed through equipment at high speeds, the front or leading edge of the sheet tended to lift up, allowing air to flow underneath the sheet. This resulted in a sheet that at least partially floated on air. The faster the swatch applying machinery was run, i.e., the more sheets per hour fed through the machine, the greater the tendency for sheets to float. The problem of sheet float has been particularly acute when lighter sheet stocks were used. The use of lighter sheet stock has tended to increase the likelihood for the sheets to lift up from the travel surfaces because the sheets do not have sufficient weight to maintain themselves in a planar alignment and against the travel surfaces. When sheets float, there has been increased occurrences of misfeeds and misprints. Floating sheets have tended to deviate from their preferred alignment, even with the assistance of the side sheet guides associated with the travel surfaces. The corners of floating sheets tended to catch on various parts of the swatch applying machinery, causing the sheets to become misaligned.
Floating sheets has limited the operating speed of swatch applying machinery. Moreover, the problem of floating sheets has been costly in terms of labor and lost production time. Labor must be expended to remove sheets that result in misfeeds or misprints. Labor must also be expended to reset the swatch applying machinery for continued production. Machinery remains idle while offending sheets are removed and the machinery reset
By engaging the sheets at their downstream edge with grabbers and then pulling the sheets through work stations mitigated a float problem, the pulling grabbers may not firmly held the entire sheet in place. Moreover, the pulling grabbers do not necessarily work well with an electronic visual inspection system because the grabbers may not mechanically engage the sheet so that it is precisely square. Further any reject system where sheet(s) are removed from the production line, the rejected sheet(s) generally have to mechanically engage with additional grabbers or pushers to remove the sheet(s). This makes the machine mechanically complex.
Accordingly, a method and apparatus are needed for directing sheets through swatch applying machinery that reduce the setup time required for changing sheet sizes, reduce problems associated with the occurrence of sheet movement from proper registration while being conveyed downstream, reduce the number of mechanical parts required to move the sheets downstream, and which allow for higher operation speeds of the swatch applying machinery and efficient inspection of the sheets during high speed production.